Fat liquoring process



- suggested for this purpose;

Patented Nov. 18, 1941 FAT LIQUOBING PROCESS Wendell H. Tisdale, Wilmington, Del., asslgnor to E. I. du Pont de Nemours & Company, Wilmin ton, Del., a corporation of Delaware Application January 13, 1940,

No Drawing.

Serial No. 313,701

7 Claims.

This invention relates to the manufacture of leather and leather products, and more particularly to leather adapted for lining shoes. Still more particularly this invention relates to methods of treating leather. to prevent growth and development of micro-organisms such as bacteria and fungus growths which otherwise would develop it the leather is moist, as with perspiration.

Leather manufacturers have been in the past distressed with the inability of their products under certain conditions to withstand micro organisms causing apparent decay and deterioration and possible infection or reinfection by growth of deleterious micro-organisms in contact with the skin as in the case of shoe linings, and divers means have been suggested for making their leathers immune to such attack. Thus, manufacturers of, high grade kid leather, especially for linings in shoes where conditions of moisture, etc., are conducive to the propagation and growth of deleterious micro-organisms, have suffered numerous and possibly unjustified complaints because of the inability of their products to withstand development of such micro-organisms. It has been proposedto avoid these objections by treating the leather with a suitable preservative adapted to prevent growth and development of the deleterious micro-organisms and many compositions and processes have been None of these proposals, however, have been entirely satisfactory whether because of the lack of a disinfectant adequate to control the micro-organisms involved or the lack of any suitable process for incorporating highly effective disinfecting agents so that the agent is retained in the leather in a manner which does not deleteriously affect the properties of the leather.

I have now found that the difficulties encountered in the prior art may be avoided by treating the leather with a water-insoluble organic mer-' cury compound or other suitable preservative in a manner such that the water-insoluble organic mercury compound is held in the leather in a non-aqueous menstruum on the fibers of the leather, and particularly I have founld that these results may be obtained if the leather is so treated that the concentration of the preservative adjacent the surface of the leather is substantially greater than the concentration at the center.

To obtain these results I treat the leather while it is substantially saturated with water, for example, while still wetfrom tannins and working operations or from dyeing and the like operations, with a solution of water-insoluble preservative in a non aqueous menstruum whereby penetration d menstruum into the leather is regulatedand controlled by the presence of water therein.

The manner of the treatment will vary according to the character of the'leather being treated. Thus, heavy vegetable tanned leathers will be subjected to-slightly different treatment than the light leathers. Similarly, crystalloid tanned leathers may require special preparatory treatment. But however applied my treatments are akin to the processes known in the art as oiling and drying, currying, hand stufiing, drum stuffing, burning-in and dipping, and fat-liquoring, in all of which processes an oil or fat is incorporated in the leather by treating the leather while it is in a wet or damp condition. In the processes of my invention I may incorporate an oil-soluble preservative in these fats and oils and thereafter carry out the treatment according tothe purposes and manners known in the art.

In carrying out the processes of my invention it is desirable to have the flesh side of the leather smooth so as to insure a uniform distribution in the leather. For the most part this is accomplished in the usual shaving machines. Also, if the skins are to be split down this should be done before treating according to my invention.

Not only do such treatments produce skins of even texture and uniform thickness but also the rolls of the shaving and splitting machines operate to squeeze out surplus water. In the case of heavy leathers, such as harness and belting leathers, the leather after bleaching and washing and preliminary treatment such as'splitting and shaving or smoothing is treated while uniformly damp with an oil solution of an oil soluble preservative. Any suitable oil, such as cod liver oil, olive oil, cottonseed oil, corn oil or mineral oils, may be used. The leather which is then uniformly coated with a thin film of the oil is hung up to dry. As the water slowly leaves the leather the oil difiuses in taking its place, and unlike oiling of dry leather the treatment gives a high concentration of preservative adjacent the surface of the leather and the leather dries without retaining an oily appearance or feel. Lighter oils, such as sulfonated castor oil, or heavier oils, such as beef tallow, may similarly be employed according to the type of leather 1 desired.

In treating light leathers, such as chrometanned goat skins, the treatment may be carried out; concurrently with the fat-liquoring operation. Chrome tanned leathers unless particularly treated as described, for example, in U. S. Patent 2,144,647, granted January 24, 1939, to John Burchill et al., are best treated while the skins are still wet from the tanning or other operations. Those skilled in the art are familiar with the various steps necessary or desirable in preparing such leathers for fat-liquoring and, moreover, are familiar with the various types of fat liquors and fat-liquoring procedures which may be used and the varying conditions which need be observed, depending upon the particular type of leather being treated and the particular facilities available in any particular plant. It is unnecessary, therefore, to describe the various methods of fat-liquoring or the various antecedent steps, such as neutralization, washing, shaving, dyeing or the like, but it is suflicient to point out that in my invention the oil component, that is, the disperse phase of the fat liquor (emulsion), may be used as the menstruum for carrying any oil-soluble preservative into the fibers of the leather and maintaining it there in the manner already pointed out. Thus oily materials, such as sulfonated neats-foot oil and raw oils including glyceride and paraflin oils, and others commonly used in fat liquors may be used as the menstruum. The oily component of the fat liquor may be replaced in part or supplemented by an oil solution of the preservative.

As a more particular example of my invention in which the parts are by weight about 400 parts of damp shaved goat skins chrome tanned and neutralized, are dyed in the usual manner and immediately after the dyeing operation are fatliquored in a fat-liquoring emulsion to which has been added about one part of a solution composed of parts phenyl mercury oleate, parts piperidine oleate, and 75 parts 110 paraflin oil. The skins are drummed in the fat liquor so prepared until practically all the fat liquor is taken up. The finished skins, which have been dried and otherwise treated, as customary in the art, and glazed with casein or other binders such as albumin, shellac, gums, etc., will contain about 0.05 to 0.075 per cent phenyl mercury oleate depending upon how completely the fat-liquor is taken up.

Instead of a self-emulsifying solution as described above I may use a dispersible emulsion such as may be obtained by emulsifying 50 parts of a twenty per cent solution of phenyl mercury oleate in 110 paraflin oil in 50 parts of an aqueous solution containing two per cent hide glue and three per cent sodium n-dodecyl sulfate.

samples of leather treated as above were tested in petrie dishes by the agar plate method and were found completely to inhibit the growth of the common molds, Aspergillus niger and Penicillium, and also common bacteria such as Staphyllococcus aureus. Not only did this treatment prevent attack of the leather by these diverse organisms but also growth was checked over a wide area surrounding the leather sample. For example, when a ten millimeter disc of the treated leather on a plate of nutrient agar was sprayed with a suspension of Staphyllococcus aureus growth was inhibited over an area 26 to 28 millimeters in diameter.

The leather thus produced is exceptionally well adapted for shoe linings, and in shoes lined therewith development and growth of deleterious micro-organisms such as common molds and infectious bacteria and fungus is prevented. The protective action shown by the agar plate tests apparently acts to prevent development of such micro-organisms as would otherwise develop in organic matterdeposited on the surface of the leather as, for example, by perspiration.

While I have described my invention with special reference to the treatment of kid leather for shoe linings, it will be understood, as already pointed out, that it is not restricted thereto but that it may be applied to various types of leather according to the various processes known in the art and as pointed out above. It will also be understood that my invention in,its broader aspects is not limited to the particular modes of treatment given above and that various modifications thereof may be made without departing from the spirit and scope of the invention so long asthe leather while wet or damp, as from a previous treating operation, is treated with a water-insoluble preservative in a non-aqueous menstruum.

The preferred menstruum is an oily material by which I mean to include fats, glyceride oils, paraflin oils, sulfonated or sulfated oils, and like oily materials commonly used in the treatment of leather. Other non-aqueous solvents, however, may be employed according to the nature of the preservative. Preferably the menstruum should also be non-volatile so as not to evaporate and deposit the preservative in the fibers of the leather. It is also preferable that the menstruum be substantially insoluble in water so that its entry into the fibers of the leather is by substitution of water rather than by solution in or mixing in the water. By water-insoluble menstruum I do not mean to exclude materials such as soaps, sulfonated oils and the like, the molecules of which are only partially soluble in water, as such materials are entirely suitable for my invention and moreover are commonly used in fat-liquoring and other treatment of leather.

The amount of water in the leather during the treatment may be varied widely according to the particular treatment involved and may range from a point at which the leather is completely saturated with water, as in a fat-liquoring operation, down to a point where as much as possible of the water has been squeezed out of the skins as a result of shaving, splitting or smoothing operations. In the case of chrome tanned leathers, except when treated as pointed out above, the leather should not be allowed to dry out prior to the treatment for in such cases it is not again possible to saturate the fibers of the leather. Thus, it is a condition of my process that the leather be treated while containing water in excess of the fiber saturation point, and

.those skilled in the art will readily understand at what point in the leather manufacture the skins will be in such condition 'or what types of dried skins on being drummed or soaked in water or otherwise treated may be brought into this condition.

Nor is my invention in its broader aspects limited to any particular preservative as any waterinsoluble preservative may be incorporated in the leather as described. So far as known, however, only organic mercury compounds are sufiiciently potent disinfectants to impart to the leather the protective and disinfecting efiects which I have described. Preferably "the preservative of my invention is an oil-soluble mercury compound of the/type described in U. S. Patent 1,993,777

The phenyl mercury compounds have been found to be most suitable for treating leather intended for linings for shoes. My invention is not so limited, however, since other water-insoluble mercurials such as phenyl mercury nitrate may be used, and in fact I may use any of the waterinsoluble mercury compounds mentioned and described in U. S. Patent 2,044,959 granted June 23, 1936, to Wendell H. Tisdale et al., and I may use any of the oil-in-water emulsions described in this patent in. which the mercury compound is carried by the dispersed phase.

I claim:

1. In the manufacture of leather the method of immunizing leather against attack by microorganisms which comprises fat-liquoring the leather with an aqueous emulsion containing a water-insoluble preservative dissolved in the dispersed phase.

2. In the manufacture of leather the method which comprises fat-liquoring the leather with an aqueous emulsion containing an organic mercury compound dissolved in the dispersed phase.

3. In the manufacture of leather the method which comprises fat-liquoring the leather with an aqueous emulsion of fat-liquor strength and composition to which has been added a small amount of an oil solution of phenyl mercury oleate, the amount of said oil solution being such that the finished leather will contain about 0.05 to 0.075% phenyl mercury oleate.

4. In the manufacture of leather the method of immunizing leather against attack by microorganisms which comprlses treating the leather during the course of its manufacture with a fatliquoring emulsion the dispersed phase of which contains a water-insoluble preservative.

5. In the manufacture of leather the method which comprises treating the leather during the course of its manufacture with a fat-liquoring emulsion the dispersed phase of which contains a phenyl mercury compound.

6. In the manufacture of leather the method which comprises treating the leather during the course of its manufacture with an oil-in-water emulsion the oil phase of which contains a phenyl mercury compound.

7. In the manufacture of leather the method which comprises treating the leather during the course of its manufacture with an oil-in-water emulsion the oil phase of which contains phenyl mercury oleate.

WE INDELL H. 'I'ISDALE. 

